(1) Field of the Invention
The present invention relates generally to a system and method for controlling a posture of a steering wheel applicable to a vehicle which achieve easiness in vehicle driver's getting on and off the vehicle.
(2) Description of the Background Art
A Japanese Patent Application First Publication Showa 61-263870 published on Nov. 21, 1986 exemplifies a previously proposed steering wheel posture controlling system.
In the previously proposed posture controlling system, the posture of the steering wheel may be modified between a driving position (an adjusted position appropriate to the driving) and a escape position (a highest limit position upto which the steering position is adjusted and is escaped for making getting on and off of the driver easy) in response to an insertion and removal of an ignition key into and from a vehicle key switch hole. In addition, the driving posture of the steering wheel can be adjusted at an arbitrary position (including the escape position). At the escape position, a space between the steering wheel and driver's seat is widened so as to enable easy getting on and off for the driver.
In a case where an air bag used for preventing the vehicle driver's body from impinging on the steering wheel due to an inertia force of the vehicle is mounted in the vehicle and the escape posture of the steering wheel is set high in order to secure a sufficient easiness in getting on and off the vehicle driver, an angle of the steering wheel with respect to a corresponding instrument panel results in a state not appropriate to the air bag operation when a tilt angle adjustment of the steering wheel is made. Then, if a weight of the vehicle driver is acted toward the steering wheel, the air bag might be expanded toward a forward direction (rear side) of the steering wheel. Therefore, in the previously proposed posture controlling system, the escape posture which can be set to the highest limit of the driving posture cannot be set so higher, the easiness in getting on and off the vehicle cannot help being sacrificed.
On the other hand, when a compatibility between an appropriate operation of the air bag and improvement in getting on and off the vehicle driver is established, it becomes necessary to press the air bag from the frontward direction by means of an auxiliary member which simultaneously operates together with an expansion of the air bag. Therefore, a structure of the periphery of the airbag and steering wheel becomes complex and the number of parts may be increased.